1. Field of the Invention
The present invention relates to an integrated gasification combined cycle power generation plant (hereafter, “IGCC”) which drives a gas turbine with flammable gas obtained by gasifying a solid fuel such as coal, and the operation control apparatus and method thereof.
2. Description of Related Art
As a power generation plant using gas turbines, an IGCC (Integrated Gasification Combined Cycle) which employs fossil fuels such as coal for fuel gas is known. With an IGCC, solid fuel is gasified by causing a high temperature gas agent to come in contact with a solid fuel in powder form in a gasifying furnace, thereby generating flammable gas. This flammable gas is then supplied to a combustor of a gas turbine, whereby the gas turbine is rotationally driven, and the rotational force thereof is transmitted mechanically to a power generator, whereby power generating is performed by power generator.
The schematics of a conventional IGCC will be described with reference to FIG. 29. FIG. 29 is a diagram illustrating a schematic configuration of the IGCC having an entrained method of gas furnace. With the IGCC in FIG. 29, coal in powder form, along with air, is supplied to a gasifying furnace 102 from a coal supplying facility 101. Char forming from carbon which is segregated from the generated flammable gas is also supplied to the gasifying furnace 102.
In the entrained method gasifying furnace 102, oxygen or air is supplied as a gasifying agent, pulverized coal and char similarly supplied are burned in a high temperature atmosphere of roughly 1500 to 1800 degrees Celsius which is greater than the ash melting point, whereby coal gas which is a flammable gas is generated. Further, upon the generated flammable gas being cooled by a heat converter configured within the gasifying furnace 102, and discharged outside of a dust removal facility 103, whereby the char remaining in the flammable gas is segregated and collected by the dust removal facility 103.
The flammable gas following the char having been segregated and subjected to dust removal is supplied to a gas clean up facility 104, whereby a sulfuric compound such as H2S (hydrogen sulfide) or COS (carbonyl sulfide), a nitrogen compound such as NH2 (ammonia), fine particles such as char, and trace components such as HCI (hydrogen chloride) and HCN (hydrogen cyanide) are removed with the flammable gas.
The flammable gas with the various components removed with the gas clean up facility 104 is supplied to a combustor 106 through a fuel supply path 105. With the combustor 106, a flammable gas is combusted with compressed air supplied from a compressor 107, whereby combustion gas is generated. The combustion gas is supplied to a gas turbine 108 from the combustor 106, and the gas turbine 108 is rotationally driven, whereby a power generator 109 having the same axis as the gas turbine 108 performs power generation.
The combustion gas having completed the process in the gas turbine 108 is exhausted to a heat recovery steam generator (HRSG) 111 as exhaust gas. Heat recovery is performed at the HRSG 111 by heat exchange with steam and the exhaust gas from the gas turbine 108. The steam subjected to heating by the heat of the exhaust gas from the gas turbine 108 is supplied to a steam turbine 112 by the HRSG 111, whereby the steam turbine 112 is rotationally driven, and a power generator 110 having the same axis as the steam turbine 112 performs power generation. The steam having rotationally driven the steam turbine 112 is condensed with the condensation device 113, and after this is supplied to the HRSG 111. Further, the exhaust gas subjected to heat recovery with the HRSG 111 is exhausted to the ambient atmosphere with the smokestack 114. The gas turbine and steam turbine described here have separate axes, but may be arranged so as to have the same axis.
A portion of the compressed air which is compressed with the compressor 107 is extracted and compressed with an axial flow compressor 115. The compressed air compressed with the axial flow compressor 115 is guided to the gasifying furnace 102. In the process wherein the compressed air is supplied to the gasifying furnace 102, oxygen which is segregated with an air separating facility 116 is mixed therein, and air with a large amount of oxygen components is supplied as a gasifying agent to the gasifying furnace 102.
On the other hand, the nitrogen which is segregated with the air separating facility 116 is supplied to the coal supplying facility 101, and is employed as a pressurizing medium or transporting medium in the event of supplying the pulverized coal and char to the gasifying furnace 102. The compressor 115 may extract a portion from the compressed air which is compressed with the compressor 107, or may obtain air from the atmosphere. The compressor 115 may be an axial flow compressor or a centrifugal compressor.
A control valve 118 to control flow quantity and pressure of the air supplied to the gasifying furnace 102 is provided in the gasifying agent supply path 117 which supplies the compressed air from the axis flow compressor 115 to the gasifying furnace 102. A control valve 120 to control the flow quantity and pressure of oxygen which is mixed into the air supplied to the gasifying furnace 102 is provided in the oxygen supply path 119 to supply oxygen from the air separating facility 116 to the gasifying furnace 102. Further, a control valve 121 to control the flow amount of flammable gas to be supplied to the combustor 106 is provided in the fuel supply path 105.
Thus, by provided the control valves 118, 120, and 121, the flow quantity of flammable gas supplied to the combustor 106 can be controlled according to load fluctuation in the gas turbine 108. That is to say, the supply quantity of pulverized coal supplied to the gasifying furnace 102 is set according to the flammable gas flow quantity supplied to the combustor 106 which is set according to the degree of opening of the control valve 121. By setting the degree of opening of the control valves 118 and 120, the flow quantity and pressure of the gasifying agent (air) necessary for gasifying the pulverized coal supplied to the gasifying furnace 102 and the oxygen mix quantity can be set. In the case that the gasifying agent is only air without increasing the oxygen mix quantity in the gasifying agent, the air separating facility 116, oxygen supplying path 119, control valve 120, and so forth, are omitted.
As described above, with a conventional IGCC, as shown in FIG. 29, a control valve 118 is disposed in the gasifying supply path 117 to supply the gasifying agent to the gasifying furnace 102, and by the control valve 118 operating as a flow-quantity adjusting valve and pressure adjusting valve, the flow quantity and pressure of the gasifying agent supplied to the gasifying furnace 102 are adjusted. Therefore, a problem can arise wherein a pressure drop with the control valve 118 can occur, resulting in plant efficiency decrease. Further, it becomes necessary to perform pressure buildup with the axial flow compressor 115, taking into account the pressure drop with the control valve 118. Therefore, setting the discharge pressure of the axial flow compressor 115 to a high pressure, as well as arranging the various supply systems to the gasifying furnace 2 as configurations to withstand high pressure, becomes necessary. Accordingly, not only does the facility design of the IGCC become difficult, but the operation thereof also has increased restrictions for provisions regarding high pressure.
The present invention has been made with the above-mentioned problems in mind, and provides an integrated gasification combined cycle power generation plant and the operation control apparatus and method thereof, wherein the pressure and flow quantity of gasifying agent to be supplied to the gasifying furnace can be controlled, and the pressure of the supply systems of the gasifying agent can have a lower pressure, and further, plant efficiency can be improved.